1. Field of the Invention
This invention relates to an apparatus for operating a lock of baking tongs of a wafer baking oven, which may also be described as an automatic wafer baking oven or a wafer baking machine, as disclosed in e.g. U.S. Pat. Nos. 4,417,508; 4,438,685; and 4,648,314.
2. Description of the Prior Art
Wafer baking ovens or automatic wafer baking ovens serve to produce rottable, preferably edible wafers by a baking of wafer dough between the baking surfaces of a wafer baking mold, which is adapted to be opened and closed and has confronting baking surfaces by which the three-dimensional shape of the baked wafers is determined. Wafer dough is initially introduced into the hot wafer baking mold when it is open and the wafer baking mold is subsequently closed and the wafer dough is baked in the wafer baking mold to form the finished wafer.
In the wafer producing industry, wafer baking ovens and automatic wafer baking ovens are used to produce identical wafers in a large quantity from a wafer dough, which in most cases is liquid. In the wafer baking ovens or automatic wafer baking ovens a multiplicity of identical wafer baking molds are received or integrated in a corresponding number of identical wafer baking tongs, which are consecutively arranged to form a star-shaped array or an endless chain and revolve through a baking space from a dough pouring station to a wafer taking station.
Such wafers may consist, e.g., of large rectangular wafer sheets, flat wafers, low hollow wafers, wafer cups, wafer plates and hollow wafers, such as cast wafer cornets and cast wafer figures. Such wafers are baked in most cases from a liquid baking dough or wafer dough, which contains no sugar or only a small proportion of sugar.
Said wafers or wafer products are fragile, crisp and brittle and have in the final product a moisture content not in excess of 0.5 to 4% and must be distinguished from soft elastic wafers, which have in the final product a moisture content in excess of 8%.
Flat wafers and low hollow wafers, such as rectangular or round wafer sheets, oblates, hollow body halves, which by means of flat webs are connected to form a single large wafer, which may be called a low hollow wafer and may have the shape of a nut, egg, acorn, cube, cylinder and the like, may be produced in wafer baking ovens or automatic wafer baking ovens, in which wafer baking molds are used which are received in baking tongs that are provided with carrying frames or such molds are integrated in baking tongs having no carrying frame. Each of said wafer baking molds consists of two flat, substantially rectangular baking plates, which are provided with lateral closing bars, which protrude from the baking surfaces. Each of said closing bars is secured to or integrated in one of the two baking plates. In most cases mutually opposite closing bars constitute venting bars, which define vent openings or vent passages permitting an escape of the water vapor which is formed in the wafer baking mold as the dough is baked therein and of the surplus dough which has been poured. As the wafer baking mold is closed, the baking surfaces of the two baking plates are caused to approach each other to leave a clearance which equals the wall thickness of the wafers which are to be baked. The wafer baking mold defines a baking cavity, which is closed at its top and bottom by the baking surfaces of the baking plates and which is laterally closed by the closing bars, which protrude from the baking surfaces. As a result, the three-dimensional shape of that baking cavity for the wafer to be baked and the three-dimensional shape of the baked wafer are determined by the two baking surfaces and the closing bars.
In the production of flat wafers and of low hollow wafers in wafer baking ovens, liquid wafer dough is poured into the hot wafer baking mold when it is open, preferably onto the baking surface of the bottom baking plate, the wafer baking mold is closed in that the top baking plate is caused to approach the bottom baking plate so as to leave a clearance which corresponds to the wall thickness of the wafer to be baked, and the dough is then baked in the closed wafer baking mold to produce the final wafer, which is taken from the wafer baking mold when it has been opened. When the wafer baking mold is closed, it is perfectly sealed except for the vent passages in the lateral closing bars and an opening of the wafer baking mold under the action of the vapor pressure which builds up during the baking process and the action of the gases produced during the baking process. This is accomplished in that when the wafer baking mold has been closed the halves of the baking tongs, which contain the baking plates, are rigidly locked by means of the lock of the baking tongs and the closed baking tongs are kept in a locked condition while they are moved through the baking space of the wafer baking oven before the wafers are taken.
In the production of cast hollow wafers, wafer baking molds are employed which can be opened and closed and which consist of a male section provided with cores, which are equal in number to the hollow wafers to be made in the wafer baking mold at the same time and correspond in shape to the desired hollow wafer, a female section, which is in most cases bipartite and formed with mold cavities which are equal in number to the cores and correspond in shape to the desired hollow wafers, and an opening and closing mechanism for moving the sections of the baking mold relative to each other. Those molds for baking hollow wafers are also received by baking tongs, which are provided with carrying frames, and are kept in a closed and/or rigidly locked state by the lock of the baking tongs during the baking process.
It is known to provide wafer baking tongs with various locks which are locked or unlocked as the closed wafer baking tongs move past a stationary operating apparatus which is mounted on the oven frame of the wafer baking oven. That opening and closing of the lock of the baking tongs, i.e., the locking and unlocking of the baking tongs, must clearly be distinguished from the opening and closing of the baking tongs, i.e. from the movement of the sections of the baking tongs away from and toward each other. The opening and closing of the baking tongs effect an opening and closing of the wafer baking mold of the baking tongs at the same time. The opening and closing of the lock of the baking tongs effects only an unlocking and locking of the baking tongs when the wafer baking mold is closed so that a spontaneous opening of the closed wafer baking mold by the pressure of the gases which are formed during the baking process in the dough which is enclosed in the wafer baking mold when the lock is closed (locked) will be prevented.
In known wafer baking tongs the lock comprises a rotatable locking mandrel, which is provided in the lock carrier of one tong member and extends at right angles to the plane of the baking plate and is provided with a hammer head at one end and with a rotary spider at the other end, and a rigid locking plate, which is provided on the lock carrier of the other tong member and is parallel to the planes of the baking plates and cooperates with the hammer head. For locking and unlocking, the locking mandrel is rotated through 90.degree. by means of a stationary stop, which is fixed to the oven frame and engages the rotary spider of the baking tongs which are passing by. The locking mandrel is held in its current angular position by means of a spring-biased ball, which enters corresponding indentations formed on the periphery of the locking mandrel.
In other known wafer baking tongs the lock consists of a cylindrical bore, which is parallel to the planes of the baking plate and is formed in one tong section in a portion thereof which is substantially at right angles to the planes of the baking plate, and a cylindrical pin, which is mounted in the other tong section and is displaceable in a direction which is parallel to the planes of the baking planes. Said pin is aligned with the bore when the baking tongs are closed and is pushed into the bore in order to lock the two tong members together.
In other known baking tongs the lock comprises a locking pin, which protrudes at right angles to the planes of the baking plates from the lock carrier of one tong section and when the baking tongs are closed extends through an opening in the lock carrier of the other tong section, and a hook, which is pivoted to the lock carrier of the other tong section and is engageable with said locking pin and is provided with an actuating member. That lock is opened and closed by means of a stationary operating apparatus, which is mounted on the oven frame and comprises a closing element, which is engageable with the actuating member of the hook in order to impart a pivotal movement to the hook and which is biased to an operative position, which corresponds to the locking position and/or the unlocking position of the hook.
The known locks of baking tongs have the disadvantage that an incomplete locking action may result in a high stress on the lock members which only incompletely interengage and this may result in a premature wear or fracture of a lock member so that long shutdown times of the wafer baking oven and high production losses may result because the members of the lock must prematurely be renewed.